1. Field of the Invention
This invention is a device for controlling the distribution of hydraulic fluid in implement control circuits of an agricultural tractor. More specifically, this invention is an improvement to a priority valve functioning to distribute fluid flow between a draft control valve and other hydraulic motors generally associated with implements attached to a farm tractor.
2. Description of the Prior Art
The priority valve body utilized in this invention is similar to valve bodies familiar in the draft control system in use by the assignee of this invention. The variable orifice and the priority spool are both completely new to this type of draft control valve however. Former embodiments were open center devices functionally different from this invention. There is no interchangeability between this invention and prior art devices familiar to the Applicant.
A flow control valve described in U.S. Pat. No. 3,770,007 entitled "Dual Direction Flow Control Valve" to Orth et al, one of the inventors also being the inventor of this invention, shows a variable orifice device that has a rotary member similar to this invention, but the similarity stops there.
Aslo U.S. Pat. No. 3,979,908 discloses a priority valve similar to the instant invention but depends on a relief valve to operate and therefore will not be able to maintain flow to a priority demand at all times as is possible with the instant invention.